An endoscope is a medical instrument for visualizing the interior of a patient's body. Endoscopes can be used for a variety of different diagnostic and interventional procedures, including colonoscopy, bronchoscopy, thoracoscopy, laparoscopy and video endoscopy.
Colonoscopy is a medical procedure in which a flexible endoscope, or colonoscope, is inserted into a patient's colon for diagnostic examination and/or surgical treatment of the colon. A standard colonoscope is typically 135-185 cm in length and 12-19 mm in diameter, and includes a fiberoptic imaging bundle or a miniature camera located at the instrument's tip, illumination fibers, one or two instrument channels that may also be used for insufflation or irrigation, air and water channels, and vacuum channels. The colonoscope is usually inserted via the patient's anus and advanced through the colon, allowing direct visual examination of the colon, the ileocecal valve and portions of the terminal ileum. Insertion of the colonoscope is complicated by the fact that the colon represents a tortuous and convoluted path. Considerable manipulation of the colonoscope is often necessary to advance the colonoscope through the colon, making the procedure more difficult and time consuming and adding to the potential for complications, such as intestinal perforation. Steerable colonoscopes have been devised to facilitate selection of the correct path though the curves of the colon. However, as the colonoscope is inserted farther and farther into the colon, it becomes more difficult to advance the colonoscope along the selected path. At each turn, the wall of the colon must maintain the curve in the colonoscope. The colonoscope rubs against the mucosal surface of the colon along the outside of each turn. Friction and slack in the colonoscope build up at each turn, making it more and more difficult to advance and withdraw the colonoscope. In addition, the force against the wall of the colon increases with the buildup of friction. In cases of extreme tortuosity, it may become impossible to advance the colonoscope all of the way through the colon.
Another problem which arises, for example, in colonoscope procedures, is the formation of loops in the long and narrow tube of the colonoscope. Such loops may arise when the scope encounters an obstacle, or gets stuck in a narrow passage. Instead of progressing, the scope forms loops within the patient. In an attempt to proceed in insertion of the colonoscope, excess force may be exerted, damaging delicate tissue in the patient's body. The physician may proceed with the attempted insertion of the endoscope without realizing there is a problem.
Through a visual imaging device the user can observe images transmitted from the distal end of the endoscope. From these images and from knowledge of the path the endoscope has followed, the user can ordinarily determine the position of the endoscope. However, it is difficult to determine the endoscope position within a patient's body with any great degree of accuracy. This becomes even more difficult when attempting to determine endoscopic positioning using, e.g., automatically controlled endoscopic devices, as described in U.S. Pat. No. 6,468,203; U.S. patent application Ser. No. 09/969,927 filed Oct. 2, 2001; U.S. patent application Ser. No. 10/229,577 filed Aug. 27, 2002; U.S. patent application Ser. No. 10/087,100 filed Mar. 1, 2002; and U.S. patent application Ser. No. 10/139,289 filed May 2, 2002, each of which is incorporated herein by reference in its entirety.
Another method used to determine the configuration of the endoscope is x-ray imaging. Yet another method used is magnetic field positioning, which avoids the x-ray exposure to the patient and the operator. Such a method typically uses magnetic position determination via low frequency magnetic fields to determine the position of a miniature sensor embedded within the endoscope tube. Based on the position of the sensor at sequential time periods, an image of the configuration of the endoscope tube is produced.
Another method involves the placement of a series of markings on the endoscope that can aid the physician in proper placement of the device in the patient's body during a procedure. These markings can include bands, dots, lettering, numbering, colors, or other types of indicia to indicate position or movement of the device within the body. Visually distinguishable marks are often located at regular predetermined intervals. Such a system of indicia can be made to be visible under fluoroscopy by the use of certain radiopaque metals, or compounds incorporated into or printed on the device.
However, each of these methods are limited in their flexibility and applicability when the position of the endoscope within a patient's body is desired with any accuracy. Furthermore, such conventional position determination methods in many cases may also fail to account for the real-time position of the endoscope during advancement and/or withdrawal into the patient.